The present invention provides molecular materials which successfully retain or have dramatically improved intrinsic physical and chemical properties of the individual molecules, such as solubility, miscibility, stiffness, adsorption property, visco-elastic property, electron mobility, fluorescent property, reactivity, aggregation property and conformation property, which can be obtained by wrapping molecules or nanoparticles with ultrathin film. The present invention also provides molecular materials which can serve as elements for constructing nano-sized organized structures in which the molecular materials can fully function just as an isolated molecule.
Molecules or molecular aggregates can exhibit their specific properties depending on the structure and composition. Molecular properties are directly expressed in a dilute solution or gaseous state. Coating or forming films of highly dispersed (solubilized) molecules on the surface of a substrate in order to utilize such molecules as functional materials, however, often results in ruining of the intrinsic properties shown by the individual molecules. This is caused by changes in the molecular properties due to inter-molecular interaction or restriction in molecular conformation due to crystallization.
To overcome the problem, there has been proposed various techniques for coating or isolating the individual molecules with proper methods. The methods include: a) spatially immobilizing molecules on the surface of solid substrates or particles, or within three-dimensional gels in order to prohibit interactions or reactions between the molecules; b) isolating molecules as guests in porous materials, layered materials, host molecules having certain internal cavities, or organized molecular assemblies; c) dispersing molecules within organic or inorganic polymers; d) enclosing molecules within molecular aggregates such as micelles; and e) including molecules within nano-structured molecules such as dendrimers.
In case that molecules are to be immobilized on the surface of a support such as solid substrates, it is necessary for the molecules to have a functional group which strongly interacts with such surface. In order to exhibit properties of the individual molecules on the surface of the support, it is also necessary to select a condition which can successfully prevent the immobilized molecules from being associated on the surface. Species of the support appropriate to the purpose and available molecules are however limited. The same will apply to the case that particles are used as the support.
The spatial immobilization of molecules within the three-dimensional gel is suitable for giant molecules but is hardly applicable to small molecules. The shape of voids and properties of porous materials are macroscopically determined by their crystal structures and cannot accommodate a wide variety of molecules. Even barrel-shaped molecules such as cyclodextrin have a strong structural specificity and can only accept a limited range of guest molecules. Water-soluble micelles can incorporate a variety of hydrophobic molecules, but its nature as a fluid molecular aggregate prevents the molecule isolated within such micelles to be used for a wide range of applications.
Certain cases have been reported where functional molecules (units) confined in the dendrimer are advantageously stabilized and would otherwise be unstable in open spaces, such as in the chemical reaction wherein low energy light is concentrated and converted it into high energy light. For such cases, it has been reported that the efficient energy transfer is ensured by the fact that the central functional molecule is isolated from the external space by the dendrimer structure, and that such dendrimer structure has an excellent rigidity. The dendrimer structure, however, needs a lot of steps for synthesis and can be obtained only in a poor yield. The challenges faced in developing desirable molecular wrapping through organic synthesis are considerable and require a great deal of work to obtain new molecular designs, synthesis, structural confirmation, and the succeeding new molecular design.
It is supposed that techniques for producing nano-precision ultrathin films is necessary for precisely covering molecule-sized materials. Such ultrathin films for covering will necessarily be conformable to every kind of molecular shape. There have been widely-known techniques for protecting active hydroxyl groups on solids or particles by reacting them with silane couplers, none of which could completely cover the molecular surface with the protective groups, so that the molecule could not completely be isolated from the external environment.
As has been described in the above, isolating the individual molecules is indispensable for fully expressing their intrinsic molecular functions. It is therefore an object of the present invention to provide molecular materials successfully retaining or being dramatically improved in the intrinsic physical and chemical properties of the individual molecules It is another object of the present invention to facilitate, through provision of such molecular materials, spatial design of molecular function, retention or improvement of properties intrinsically owned by the isolated molecule, thorough expression of the functions attributable to the molecular structure, construction of functional materials on solid substrates, and manipulation of molecules.
The present inventors found out after extensive investigations that the foregoing objects can be accomplished by using nano-wrapped molecular materials comprising molecule, molecular aggregate or nanoparticle which has the surface at least partially covered with an ultrathin film containing oxygen-metal bond. The present invention is to provide also nano-wrapped molecular materials comprising a plurality of molecules, molecular aggregates and/or nanoparticles covered with a single continuous ultrathin film containing oxygen-metal bond. The materials also include such that comprising a plurality of molecules, molecular aggregates and/or nano-particles which are thoroughly dispersed inside of a single ultrathin film containing oxygen-metal bond.
In the nano-wrapped molecular materials of the present invention, the molecule, molecular aggregate, or nanoparticle is preferably bound with the ultrathin film through chemical bond, physical bond, or electrostatic bond. The molecule, molecular aggregate, or nanoparticle may be wrapped with two or more layers of such ultrathin film, where the total thickness of such wrapping film is preferably 0.5 to 100 nm.
It is preferable that the molecule, molecular aggregate, or nanoparticle is physically isolated from solvent molecule in a partial or extensive manner, and has solubility. In particular, it is preferable that the molecule, molecular aggregate, or nanoparticle is covered with the ultrathin film to an extent which does not cause substantial changes in the properties of such molecule, molecular aggregate, or nanoparticle due to interaction between the molecules or nanoparticles. The nano-wrapped molecular materials of the present invention may also have reactive outer surfaces.
The nano-wrapped molecular materials of the present invention are preferably such that being covered through hydrolysis and condensation reaction of metal alkoxide compounds. Examples of the nano-wrapped molecular materials include such that having the ultrathin film formed by binding metal alkoxide compound to at least a part of active groups, which exist on the surface of the molecule, molecular aggregate or nanoparticle, that has reactivity with such metal alkoxide compound, and then by hydrolyzing the product to thereby condense the metal alkoxide compound; such that having the ultrathin film formed by binding metal alkoxide condensate that formed by condensing a plurality of metal alkoxide molecules to at least a part of active groups, which exist on the surface of the moleculer molecular aggregate, or nanoparticle that has reactivity with such metal alkoxide compound; such that having the ultrathin film formed by allowing at least apart of cationic charges, which exist on the surface of the molecule, molecular aggregate, or nanoparticle, to interact in an electrostatic manner with a condensate of silanol-group-containing compound; and such that having the ultrathin film formed by allowing at least a part of hydrogen-bond-formable groups, which exist on the surface of the molecule, molecular aggregate, or nanoparticle, to interact through hydrogen bonding with a condensate of silanol-group-containing compound